As appreciated by those of skill in the art, it is often beneficial to administer therapeutic or diagnostic agents (herein referred to variously as "medicaments", "medications", or "drugs") to the lungs or through the lungs of a patient. For certain medical conditions, topical administration of medication to the lung is often the preferred way to provide relief to the patient. For example, in the case of an acute asthma attack, direct "rescue" administration of medications such as albuterol directly to the smooth muscle of a patient's lungs provides for immediate relief of bronchial inflammation.
Systemic delivery or administration of medicament by inhalation to the blood stream via the alveolar blood vessels, may also provide advantages over standard oral or intravenous systemic delivery regimes. For example, in comparison with oral dosing, systemic delivery via the lung can increase bioavailability of some medications by avoiding metabolic inactivation of the medicament in the gut or liver. Respiratory delivery to the blood stream also avoids the potential risk of disease transmission from using intravenous delivery devices such as hypodermic needles.
Many devices exist in the art which are useful for delivering medicaments via the inhaled route, including propellant based metered dose inhalers (MDIs). Due to environmental concerns over ozone depletion, MDIs using chlorofluorocarbons as propellants are being phased out in favor of more environmentally friendly powder inhalers.
Dry powder inhalers, which lack any propellants whatsoever, are viewed as one solution to the alleged problem caused by ozone depleting propellants. Dry powder inhalers are of three basic varieties: Reservoir based Dry Powder Inhalers (RDPIs); Multi-unit dose Dry Powder Inhalers (MDPIs); and Unit dose Dry Powder Inhalers (UDPIs). RDPIs meter doses in the device out of a powder reservoir to provide multiple doses of medication, while MDPIs contain multiple premeasured, individually packaged doses of drugs. UDPIs, in comparison, contain a single dose of medicament.
Despite the desirability of drug delivery via inhalation and the preferability of dry powder inhalers, it is often difficult to obtain a patient's full compliance with prescribed instructions for an inhaled medicament, and reasons for non-compliance may vary. Patients may fail to fully comply with prescribed dosing because of awkwardness of the size or shape of their inhaler. The dry powder inhalers currently known in the art, for the most part, tend to be bulky and, therefore, awkward to carry on one's person. The awkwardness of carrying such devices contributes to a patient's failure to have the inhaler available during daily activities. For some individuals in need of "rescue" applications of medication, such as patients with severe asthma or athletes experiencing exercise-induced asthma attacks, this can be a significant disadvantage to inhaler design. Bulky, cumbersome inhalers are ill-suited for such purposes.
Another reason patients might not comply with prescribed dosing is that they may perceive a social stigma from using their inhalers in public. In some cases, patients may feel embarrassed or self-conscious about using a cumbersome inhaler in public places and therefore, may not carry and/or use the inhaler as prescribed by their doctors.
A still further reason for patients not using inhalers may include the patient's inability to afford the devices at all due to limited financial resources. Complexity of a device adds to its cost, and the more expensive a device is, the less accessible it may be to all potential users.
UDPIs are generally speaking less complex, more compact and less expensive than RDPIs and MDPIs. Moreover, RDPIs and MDPIs are not ideally suited for delivering therapies only needing a single application, especially where disposability after use is a desirable feature. Prior art UDPIs, unfortunately, in some instances remain relatively bulky and awkward and may be made from environmentally unfriendly, non-biodegradable materials, such as certain plastics.
Examples of prior art UDPIs include that disclosed in U.S. Pat. No. 5,645,051 to Schultz, which describes a plastic and metal unit dose dry powder inhaler having a motor driven impeller. PCT Patent Publication No. WO 97/05918 to Asking discloses a UDPI having a dry powder dose sandwiched between two peelable cover strips. The cover strips are pulled from the device, thus internally exposing the drug in a flow path. PCT Publication No. 96/222802 assigned to Directhaler discloses a straw-like UDPI having a dose contained within the straw and which is sealed by removable end caps.
Despite the existence of various prior art unit dose dry powder inhalers, there remains much room for improvement in the art. Specifically, there exists a long-felt need for a UDPI apparatus and method of use wherein the inhaler apparatus is inexpensive, disposable, environmentally friendly, simple, compact and easily carried and used by a patient, so as to increase patient compliance, and yield improved drug delivery.